State space Representation and Transfer function don't match?

Hi everyone,

I don't understand why the state space output doesn't match the transfer function model in Simulink.

I am sure that the PI controller is able to make the value converge to the one i need (30) in this case, but in the state space representation the output value doesn't converge to 30 and i don't understand why.

The values for the simulink models are the following:

J_M=0.00009;

B_M=0.01;

Lambda_PM=0.14294;

polepairs=3;

L=2.2e-4;

R=4.46;

a=-B_M/J_M;

c=1;

b=1.5*polepairs*Lambda_PM;

d=0;

The simulink file is attached, together with the results i get from it.

Thank you in advance :)

[Mathieu NOE]

hi

could not run the simulink file because I have R2020b

but I noticed the two systems do have significant difference in DC gain - why not make things simpler and have same gain ? then you could use also same PID

% ss step response
figure(1),step(a,b,c,d)

% tf step response
num = b;
den = [J_M B_M];
figure(2),step(num,den)

[Claudio Di Pietro]

You are totally right Mathieu! I messed up the ss model parameters.

Merci beaucoup for the hint :)

[Mathieu NOE]

My pleasure

Ciao